Analysis of Inertia Characteristics of Direct-Drive Permanent-Magnet Synchronous Generator in Micro-Grid

Abstract

Micro-grid has received extensive attention as an effective way to absorb new energy. Compared to large power systems, the micro-grid system consisting of power electronics is relatively weak due to the lack of support for synchronous machines. In this paper, the direct-drive wind turbine (WT) is connected to the low-inertia micro-grid as the research background. Based on the virtual inertia control of the WT, the inertia source and the physical mechanism of the WT connected to the micro-grid system are studied. The inertia characteristics of the rotor of the WT on the electromechanical time-scale, the DC side capacitor on the DC voltage time-scale, and the simulated grid under the droop control are analyzed. The research results show that under the control of the system, the inertia of the system is derived from the WT, DC capacitor, and the micro-grid simulated by droop control converter. The equivalent inertia of each link is determined by the control parameters, steady-state operating point, and structural parameters. The resulting inertia characteristics will have frequency domain characteristics under control. Finally, the correctness of the system inertia analysis conclusion is verified by simulation and experiment.

Disturbance-Suppression Method of Direct-Driven PMSG-Based Wind Power System in Microgrids

“…The assumptions adopted in this paper are consistent with those in [6]. From the stator flux and the stator voltage equations, the mathematical model of the DPMSG in the dq frame can be obtained as follows where Ψ f is the rotor flux linkage of the DPMSG, e sd and e sq are the stator terminal voltage in the dq frame, R s is the stator winding resistance, L sd and L sq are the inductances of the direct and quadrature axis.…”

“…However, the DPMSG-based WPS has the characteristics of dispersion, randomness and volatility, which makes the microgrid prone to three-phase asymmetry of the voltage and current, resulting in a decline in the power quality of the microgrid [3][4][5]. Therefore, a strong ability to suppress unbalanced disturbances is required in the DPMSG-based WPS connected to the microgrid [6,7]. To this end, it is necessary to accurately detect the state information in the transient process and quickly suppress disturbances by the control technology, so as to improve microgrid stability.…”

RoCoF Droop Control of PMSG-Based Wind Turbines for System Inertia Response Rapidly

“…As shown in Table 1, exceeding the threshold values will trigger the related protection devices for frequency deviation and RoCoF [4][5][6][7][8]. However, with the booming of low-inertia and underdamping direct drive wind turbine generator, the resultant reduction in the installed capacity and rotating inertia ratios of rotary synchronous generators (RSG), and relatively weaker dynamic support capability, which further deteriorates the grid frequency deviation and RoCoF characteristics, are not conducive to the system frequency stability [9][10][11][12][13].…”

Virtual Inertia-Based Inverters for Mitigating Frequency Instability in Grid-Connected Renewable Energy System: A Review

“…Renewable energy sources (RES) is much preferred because of its merit factors, including cost-effectiveness, energy efficiency, and sustainability [2]. The tremendous growth of RES gravitates modern power grid towards the inverter dominated power system [3], from the conventional synchronous generator (SG) rotational generator dominated power system [4]. Grid-connected or grid-tied RES is beneficial in improving the voltage profile, increasing the reliability of the power system, and controlling the active and reactive power flow [5].…”

“…,(4) and(6) are discretized and solved in each control cycle in a digital controller, including microcontroller unit (MCU) and digital signal processor (DSP) to generate the gating PWM signals. The inverter output current (i) and grid voltage (v) are the feedback signals to solve the differential equations within the controller.…”